This section provides background information related to the present disclosure which is not necessarily prior art.
Conventional footwear typically includes an upper structure and a sole structure that cooperate to support a foot during use. The upper structure securely receives and positions the foot while the sole structure, which is typically secured to a lower portion of the upper structure and generally between the foot and a ground surface, attenuates reaction forces by absorbing energy as the footwear contacts the ground.
In addition to positioning a foot and absorbing energy during use, modern articles of footwear also concurrently provide a user with comfort, style, and enhanced athletic performance. For example, in one configuration, athletic footwear may provide a long-distance runner with support and comfort during use while concurrently enhancing the ability of the athlete to run long distances. Such a balance between function (i.e., support and comfort) and performance is often achieved by selecting materials that provide adequate support to a foot during use while concurrently being relatively light in weight.
In an effort to strike an optimum balance among support, comfort, style, and performance, footwear manufacturers have recently not only varied the materials chosen for the upper structure and for the sole structure, but have also separated the sole structure into two unique zones: a metatarsal head or forward region disposed proximate to the ball of a foot and a calcaneus or heel region disposed proximate to the heel of the foot. Separating the sole structure into two discrete regions allows manufacturers to tailor the performance of each region through material selection and/or structure.
Separating the sole structure into the forward region and heel region also allows footwear manufacturers to incorporate materials into the respective regions that are appropriate for each region. For example, a footwear manufacturer may incorporate a somewhat flexible material into the forward region along with an accompanying segmented structure that cooperate to allow the forward sole structure to flex in response to bending of a foot during walking or running. A similar approach may be applied to the heel region, which may incorporate an air bladder or other shock-absorbing columnar structure that is used in conjunction with a relatively hard material disposed on an undersurface of the heel region to absorb and cushion impact of a heel during walking or running.